Planting clematis - distance?

We are putting up a (free-standing) trellis approx. 1.8m high by 2m wide and want to grow clematis. I haven't grown them before so I wonder how many plants maximum could I plant up, i.e. what kind of distance between the plants? Was hoping to plant 3, one of each group, possible 4, or would that be squeezing it?

I often plant two group 2s or group 3s together on trellis or obelsiks to get a contrast of colour and flower shape and it works well. Putting two different pruning groups together would be a pruning nightmare.

I often plant two group 2s or group 3s together on trellis or obelsiks to get a contrast of colour and flower shape and it works well. Putting two different pruning groups together would be a pruning nightmare.

Like Nut and Obelixx I keep my group2's and group3's on separate structures - it is easy to just cut the group 3's right back in spring if there is nothing else on the trellis. They also suggest getting some flat tiles to put round the stem of the plants when you have planted them - it keeps the roots shady, whilst the rest of the plant is in the sun.

Look forward to seeing phots of the results - clematis are one of my favourites ! Good luck

Thanks chicky, and thanks to obelixx that's very helpful, yes I will definitely stick to keeping the pruning groups separate. Can't wait to get stuck in soon - I feel like a kid in a candy shop, there's so much choice!